In the field of protein research, for the analysis of protein structure and function, a large amount of protein is expressed using cDNA, and the thus obtained recombinant protein is separated and purified.
Proteins translated from genes undergo various posttranslational modifications such as phosphorylation and glycosylation to regulate the function thereof. Such posttranslational modifications are involved in intracellular communication, cell-cycle regulation, metabolic control, and the like, and therefore are important cell regulatory mechanisms. In order to research such mechanisms of protein regulation, there is a demand for development of means for separating a non-modified protein and a modified protein from one another for purification.
Meanwhile, hydroxyapatite has excellent biocompatibility, and has been heretofore widely used as an adsorbent in a column (that is, in an adsorption apparatus) for liquid chromatography to adsorb and separate a protein etc (see, for example, U.S. Pat. No. 4,781,904).
However, an adsorbent made of hydroxyapatite non-specifically adsorbs various proteins, and therefore there is a problem that it is difficult to allow such an adsorbent to selectively adsorb a specific protein. For this reason, such a conventional adsorbent made of hydroxyapatite is not suitable for use in separation of a non-modified protein and a modified protein from one another for purification.